"three" sent me the mobile phone booster box which plugs in to the router.
well this is how it went. says set up takes 10 mins to an hour to configure itself well took around 18 hours for me, then the mobile works perfectly but every so often it reverts to configuring itself and hangs making the phone unusable. the answer to restart the router where it resets reasonably quickly.
has small lights to indicate status red = not working flashing green = configuring green = working
worth getting if you have poor or weak signal at home, supplied free.